Since the discover of carbonic anhydrase (CA) in ox red cells by Roughton and his colleagues 50 years ago, considerable data have accumulated concerning the structural characterization of the genetically distinct forms (isozymes) of CA as well as their physiological significance, hormonal control, tissue and cellular localization within and between species, developmental patterns, comparative kinetics, inhibition by sulfonamides, and genetic control and evolution. However, as yet no conference has been held which has been devoted entirely to the biology and chemistry of the CA isozymes. With the discovery of two different isozymic forms (Ca I and CA II) of CA some 20 years ago, there was a resurgence of inerest in research on CA at all levels. The recent discovery of a third isozyme of CA (CA III) which is primarily expressed in skeletal muscle has renewed curiosity about the diverse physiological roles of the CA isozymes. Because of these discoveries, a number of unresolved problems and controversial issues have arisen dealing with such matters as the nature of the active site mechanism, the physiological roles of the 3 CA isozymes in different tissues, the hormonal control of CA levels, the exact cellular and subcellular localization of specific CA isozymes, the evolutionary origins of the CA isozymes, the developmental patterns of CA expression, and the structure and organization of the CA isozyme genes. With a view toward helping to resolve some of these problems as feel it is important to bring together investigators who are actively working in these areas. Also, it is hoped that such studies on the CA isozymes will make it an important model system to help in understanding just how enzymes which arose from a common ancestral gene may evolve separate functions under different selective pressures, ultimately assuming diverse activities and functions, the disruption of which could lead to clinical abnormalities. It is our intention to rapidly publish the conference findings; thereby providing a valuable source book for students, clinicians and researchers who would like an authoritative reference to the recent important developments in CA research.